The Providence Journal’s sister paper, the Dallas Morning News, will begin charging readers to access some of its content online next month, the paper reported today – and the Morning News’ plan may signal what The Journal’s “Diet Projo” paywall plan will look like when it starts later in the year.

The Morning News will offer two subscription packages:

Print+digital: The price of a print subscription, which buys delivery of the newspaper plus full access to its digital offerings, rose 13% to $33.95 per month ($407 annually) on New Year’s Day. That’s slightly less than a Journal subscription, which currently costs $416 a year.

Digital-only: The price of a digital subscription – which buys a daily e-edition, stories behind the paywall on DallasNews.com, and iPad and iPhone app access – will be $16.95 per month, or $203 annually.

So what’s going to go behind the paywall and what will remain available to anybody? “Subscriber content will include proprietary news and information produced by The News,” the paper explained. “Headlines, breaking news, most blogs, obituaries, classifieds and nonproprietary content such as syndicated wire stories will remain free.”

The Morning News’ iPhone and iPad apps, which will use The New York Times’ new Press Engine platform, will launch on Jan. 18, the same day a redesigned version of its website goes live. (The Projo’s apps and a new Projo.com are also supposed to debut later this year.) The Morning News says it’s working on Android and BlackBerry apps, too.

A free trial period for all the Morning News’ digital content will take place from Jan. 18 to Feb. 14. After that, online readers will be asked to subscribe if they want full online and mobile access.

“Newsonomics” author Ken Doctor, whom I interviewed for my story last week about the Projo’s valuation, told the Morning News he expects about six major metropolitan daily papers to be charging by midyear. The New York Times and the NYT-owned Boston Globe both plan to start doing so within a few months.

“If the product is substantial enough and meaningful enough in people’s lives, then I think they’re willing to pay for it,” Doctor said. “The biggest question I think is metros that have cut back so substantially that they have brought into question their value proposition to their readers.”

Update: The paywall announcement wasn’t the only news out of A.H. Belo. The company also said it has finished splitting its pension plan off from regular Belo (which spun off its newspapers into A.H. Belo in 2008).

I’m not an expert on corporate pension accounting, but the Morning News’ story on the transaction implies that A.H. Belo will need to fork over $53 million to its pension fund this year. That would be about 65% of the $81 million in cash and equivalents the company had stockpiled as of Sept. 30, which may help explain why A.H. Belo’s execs have been so hesitant about spending that money.